Comparison of complement fixation and phenotypic mixing tests for the detection of lymphoid leukosis virus in egg albumen and embryos of individual eggs

Reflections on the pathogenesis of diseases caused by the acute avian leukosis/sarcoma viruses with special reference to avian erythroblastosis

The various diseases that follow experimental infection with the acute and non-acute avian oncoviruses are discussed with special reference to the pathogenesis of avian erythroblastosis. One view, based on in vitro studies, sees erythroblastosis as the product of a failure in the differentiation of virus-infected stem cells to mature erythrocytes, as a result of cell 'transformation'. The results of some in vivo studies, however, point to a resemblance of the disease to a haemolytic anaemia, where cellular death is an important component. It seems probable that the disease is the result of transformation of cells of the erythroblastic series followed by the death of many of these cells due to influences that have not yet been determined. Determination of the causes of this cellular death may prove to be as important for our understanding of the problem of leukaemia as the work that has already been accomplished in explaining the causes of cell transformation. It is also suggested that the tendency of gs amino acid sequences of the avian leukosis viruses and mouse leukaemia viruses to form fusion proteins with a variety of proto-oncogenes may be part of a wider phenomenon, and that these sequences may fuse with other proteins, altering their properties. More work is required on the possibility that there is an undiscovered immunological component in the progression of the L/S diseases.

Relative efficiency of test procedures to detect lymphoid leukosis virus infection

A total of 2544 comparisons were used to study the relative efficiency of various test procedures currently used to detect lymphoid leukosis virus infection in chickens. Meconium, blood, cloacal swabs, and egg albumen were collected from day-old chicks and adult hens from four breeder flocks. The phenotypic mixing was used as the biological assay for infectious virus. The complement fixation test and enzyme-linked immunosorbent assays were used as direct assays for the group-specific antigen of the avian leukosis-sarcoma viruses. Analysis of test results of biological assays has shown that blood from virus-infected chicks was more frequently positive than meconium. Also, direct assay for group-specific antigen was as efficient as the biological assays for detection of positive albumen samples from freshly laid eggs. The rate of false-positive reactors recognized by direct assays was lower in albumen samples than in cloacal swabs collected from hens that produce endogenous virus or group-specific antigen. Data also showed a relatively high concordance, ranging from 71 to 100%, between various assays with test materials from adult hens. Progress in reducing rates of exogenous lymphoid leukosis virus infection can be significant if dams are selected on the basis of any one of the test procedures examined. For complete eradication however, day-old chicks should be selected on the basis of the biological assay of blood of individual chicks reared in small groups.